The invention pertains to the field of devices for dispensing dry materials and, more particularly to a portable battery-powered spreader for particulate materials such as may be used for garden dusting or fertilizing.
Many mechanical devices exist that aid in the even dispensing and spreading of particulate material such as insecticide or fungicide dusts or granular particulate materials such as fertilizers. The simplest hand-held spreaders for granulated products are manually operated by a rotary crank which either directly or indirectly turns a rotor which dispenses the particulate material from a hopper on the apparatus. U.S. Pat. No. 4,140,280 discloses one such apparatus. A portable battery-operated apparatus for such use is disclosed by U.S. Pat. No. 3,993,225. A somewhat different approach is disclosed in U.S. Pat. No. 4,678,377, in which a powder is contained in a flexible and manipulable pouch open at two ends through which a flow of air is forced by the drive mechanism to eject the dust.
One problem encountered in any mechanism for the dispensing of powdered material is the tendency of the material itself to lump and clog (as described in U.S. Pat. No. 4,712,716, which discloses a mechanism for metering dusting powder to assure even flow) or to bridge (as described in U.S. Pat. No. 4,071,170).
U.S. Pat. No. 4,071,170 discloses a portable motor-driven dusting apparatus which incorporates a mechanism to agitate the powdered material as it is being fed to the rotary blower to assure uniform rate of flow and avoid clogging or bridging problems.
U.S. Pat. No. 5,199,993 discloses a battery-powered spreader for dispensing either dust-like or granular particles such as insecticides or fertilizer, respectively.
In battery-powered spreaders of the prior art, the particulate material is introduced directly to the blower so that the flow of air and material passes directly through the blower vanes. Especially with larger and heavier particles, the moving blades have a tendency to impact the particles resulting in unpredictable impact trajectories and ultimately providing a nonuniform discharge pattern. This also entails a number of wear-related problems and thus limits the spreaders' use with particulate material having physical or chemical properties which might damage or interfere with the blower.
The situation is exacerbated when the spreader is designed so that the blower is turned on simultaneously with the opening of the valve which controls flow of material from the reservoir. On starting, this may cause material to accumulate in the blower before the blower can get up to speed, and upon stopping, may leave accumulations of material in the blower. Large accumulations of material may stall the motor. Additionally, the action of the blower may be injurious to the particulate matter which is to be spread. This is especially important in the case of seeds which may have a fragile nature.